Posture estimation system, posture estimation apparatus, error correction method, and error correction program

ABSTRACT

A posture estimation system includes: a marker that is mounted on an object; a camera that captures an image of the object; an analysis section that analyzes a posture of the object on a basis of a position of the marker included in a captured image captured by the camera; an inertial measurement section that is provided on the object to detect motion of the object; a calculation section that calculates calculated posture information indicating the posture of the object on a basis of detection information indicating a detection result from the inertial measurement section; an estimation section that estimates the posture of the object on a basis of the calculated posture information and analyzed posture information indicating the posture of the object analyzed by the analysis section; and a correction section that corrects an error included in the calculated posture information on a basis of the analyzed posture information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2019-092809 filed May 16, 2019, the entire contents ofeach of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a posture estimation system, a postureestimation apparatus, an error correction method, and an errorcorrection program.

A motion capture system has been known that extracts motion of a subject(see, for example, Japanese Patent Laid-open No. 2017-53739).

A motion capture system described in Japanese Patent Laid-open No.2017-53739 includes a marker mounted at a feature point on the subject,a plurality of cameras, an information processing apparatus, and adisplay apparatus.

The plurality of cameras are provided to surround a movable range of thesubject and chronologically captures images of the marker. Imageprocessing apparatuses processes captured images chronologicallyreceived from the plurality of cameras to calculate coordinates of themarker in a three-dimensional space, that is, three-dimensionalinformation. The display apparatus includes a feature informationextraction section and receives information from the image processingapparatus. The feature information extraction section calculates, fromthree-dimensional chronological position information regarding themarker, a particular physical quantity at each chronological position ofthe marker to calculate a stride width, a walking speed, and a landingtime of the subject, which correspond to feature information regardingthe motion of the subject.

SUMMARY

In recent years, a suggestion has been made about estimation of theposition and posture of the subject based on the position and posture ofthe subject measured by the motion capture system as described above andthe position and posture of the subject calculated on the basis ofdetection results from an Inertial Measurement Unit (IMU) mounted on thesubject to detect an acceleration and an angular speed.

However, in regard to an acceleration sensor and a gyro sensor includedin the inertial measurement unit, detection results from the gyro sensorinvolve errors accumulated over time due to properties of the gyrosensor. Thus, the actual posture of the subject may deviate from theestimated posture.

It is desirable to solve at least some of the above-described problems,and it is also desirable to provide a posture estimation system, aposture estimation apparatus, an error correction method, and an errorcorrection program that can reduce errors in the estimated posture of anobject.

According to a first aspect of the present disclosure, a postureestimation system is provided that includes a marker that is mounted onan object, a camera that captures an image of the object, an analysissection that analyzes a posture of the object on a basis of a positionof the marker included in a captured image captured by the camera, aninertial measurement section that is provided on the object to detectmotion of the object, a calculation section that calculates calculatedposture information indicating the posture of the object on a basis ofdetection information indicating a detection result from the inertialmeasurement section, an estimation section that estimates the posture ofthe object on a basis of the calculated posture information and analyzedposture information indicating the posture of the object analyzed by theanalysis section, and a correction section that corrects an errorincluded in the calculated posture information on a basis of theanalyzed posture information.

According to another aspect of the present disclosure, a postureestimation apparatus is provided that includes a communication sectionthat externally receives first posture information indicating a postureof an object, an input section that receives detection informationindicating a detection result from an inertial measurement unit providedon the object, a calculation unit that calculates, on a basis of thedetection information, second posture information indicating the postureof the object, an estimation section that estimates the posture of theobject on a basis of the first posture information and the secondposture information, and a correction section that corrects, on thebasis of the first posture information, an error included in the secondposture information.

According to yet another aspect of the present disclosure, an errorcorrection method for correcting an error included in informationindicating a posture of an object is provided, the error correctionmethod includes correcting, on a basis of first posture informationindicating the posture of the object and externally received, an errorincluded in second posture information indicating the posture of theobject calculated on a basis of a detection result from an inertialmeasurement unit provided on the object.

According to still another aspect of the present disclosure, an errorcorrection program executed by an information processing apparatus andcorrecting an error included in information indicating a posture of anobject, the error correction program causes the information processingapparatus to correct, on a basis of first posture information indicatingthe posture of the object and externally received, an error included insecond posture information indicating the posture of the objectcalculated on a basis of a detection result from an inertial measurementunit provided on the object.

According to the above-described configuration, the error included inthe detection result from the inertial measurement unit can be used toreduce a deviation between the posture of the object calculated on thebasis of the detection result and the actual posture of the object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of an imagedisplay system according to an embodiment of the present disclosure;

FIG. 2 is a block diagram illustrating a configuration of an imagedisplay system according to the embodiment;

FIG. 3 is a plan view illustrating an example of arrangement of aplurality of cameras according to the embodiment;

FIG. 4 is a block diagram illustrating a configuration of a terminalapparatus according to the embodiment;

FIG. 5 is a block diagram illustrating a functional configuration of acentral processing unit (CPU) according to the embodiment;

FIG. 6 is a diagram illustrating an input timing for detectioninformation and a reception timing for analysis information according tothe embodiment;

FIG. 7 is a flowchart illustrating error correction processing accordingto the embodiment; and

FIG. 8 is a flowchart illustrating error correction processing accordingto the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present disclosure will be described below on thebasis of the drawings.

[General Configuration of Image Display System]

FIG. 1 is a schematic diagram illustrating a configuration of an imagedisplay system 1 according to the present embodiment. FIG. 2 is a blockdiagram illustrating a configuration of the image display system 1. Notethat FIG. 1 illustrates the configuration in which two users US areassumed to be in a three-dimensional space SP but that FIG. 2illustrates the configuration in which one user US is assumed to be inthe three-dimensional space SP.

The image display system 1 according to the present embodiment includesa posture estimation system and presents a user corresponding to anobject positioned in a three-dimensional space with images correspondingto the position and posture of the user. Specifically, the image displaysystem 1 is a Virtual Reality (VR) system or an Augmented Reality (AR)system setting a viewpoint in a virtual space according to the positionand posture of the user in the three-dimensional space and displaying,to the user, an image of the virtual space drawn on the basis of the setviewpoint. Such an image display system 1 can be applied to a match-typefighting game in which, for example, a plurality of users US (US1 andUS2) fight each other as illustrated in FIG. 1.

As illustrated in FIG. 1 and FIG. 2, the image display system 1 includesa display apparatus 2, an inertial measurement unit 3, a camera system4, and a terminal apparatus 8.

[Configuration of Display Apparatus]

The display apparatus 2 corresponds to a display section mounted on eachof the users US to display input images. Specifically, the displayapparatus 2 displays images input from the terminal apparatus 8 suchthat the user US can view the images. In the present embodiment, thedisplay apparatus 2 includes a Head Mounted Display (HMD) mounted on ahead HD of the user US. In particular, the display apparatus 2 is anon-transmissive head mounted display provided with the display sectionin front of the eyes of the user US to display images and configured toprevent an outside world from being observed. Specifically, the imagedisplay system 1 according to the present embodiment is a VR system.However, the display apparatus 2 is not limited to the non-transmissivehead mounted display but may be a transmissive head mounted display. Inthis case, the image display system 1 can be configured as an AR system.Besides, the display apparatus 2 may be a display apparatus that can becarried by the user US, for example, a smartphone.

[Configuration of Inertial Measurement Unit]

The inertial measurement unit 3 corresponds to an inertial measurementsection. The inertial measurement unit 3 is provided on the head HD ofeach of the users US to detect motion of the user US. In the presentembodiment, the inertial measurement unit 3 is provided on the displayapparatus 2 mounted on the head HD to particularly detect the head HD ofthe user US.

The inertial measurement unit 3 detects accelerations in three axes andangular speeds in three axes at a predetermined sampling rate.Specifically, the inertial measurement unit 3 includes a tri-axisacceleration sensor and a tri-axis gyro sensor. In the presentembodiment, the sampling rate at which the acceleration and the angularspeed are sampled by the inertial measurement unit 3 is 1000 frames persecond (fps).

The inertial measurement unit 3 is connected to the terminal apparatus 8through a cable to output, to the terminal apparatus 8, detectioninformation including detected accelerations and angular speeds. In thiscase, the inertial measurement unit 3 outputs a time stamp obtained atthe time point of detection of the accelerations and angular speeds andincluded in the detection information. Note that the time stamp may be adetection time or information indicating elapsed time from activation ofthe image display system 1.

[Configuration of Camera System]

The camera system 4 is a motion capture system processing a capturedimage of each of the users US in the three-dimensional space to analyzethe position and posture of the user US. As illustrated in FIG. 1 andFIG. 2, the camera system 4 includes, in addition to a plurality ofmarkers 5 and a plurality of cameras 6, a server 7 serving as ananalysis apparatus as illustrated in FIG. 2.

[Configuration of Makers]

The plurality of markers 5 are provided on respective positions on thebody of each of the users US, and images of the markers 5 are capturedby the plurality of cameras 6. The plurality of markers 5 are providedat positions where the motion of the user US can be detected when theuser US moves. Examples of the regions of the body of the user US withwhich the markers 5 are provided include the head, the backs of theright and left hands, the tops of the right and left feet, and thetorso.

The markers 5 may each be shaped like a sphere including a semi-sphereor like a sheet.

[Configuration of Camera]

FIG. 3 is a plan view illustrating an example of arrangement of theplurality of cameras 6.

As illustrated in FIG. 3, the plurality of cameras 6 are provided atregular intervals surrounding the three-dimensional space SP set as amovable range of each of the users US. In the present embodiment, as theplurality of cameras 6, eight cameras are provided on the periphery ofthe three-dimensional space SP with an image capturing direction of eachof the cameras facing the interior of the three-dimensional space SP.Note that the number of cameras 6 can be appropriately changed.

The plurality of cameras 6 transmit captured images to the server 7. Inthe present embodiment, each camera 6 has an image capturing rate of 200fps.

[Configuration of Server]

The server 7 includes an analysis section 71 analyzing the motion ofeach of the users US in the three-dimensional space SP on the basis ofcaptured images transmitted from the plurality of cameras 6.

Specifically, the analysis section 71 analyzes the position and postureof the user US in the three-dimensional space SP on the basis ofvariation in the positions of the markers 5 obtained by chronologicallyprocessing captured images. The analysis section 71 acquires analysisinformation including analyzed position information indicating theanalyzed position of the user US and analyzed posture informationindicating the analyzed posture of the user US. The server 7 thenwirelessly transmits the analysis information to the terminal apparatus8 provided on the user US to be analyzed. At this time, the server 7transmits a time stamp indicating the timing of capturing of thecaptured image for which the analysis section 71 has analyzed theposition and the posture, the time stamp being included in the analysisinformation. In other words, the analyzed posture information includesthe time stamp. Note that the analyzed posture information correspondsto first posture information and that the analyzed position informationcorresponds to first position information.

Note that the time stamp may be the time of image capturing of thecaptured image used for the analysis of the position and posture by theanalysis section 71, or information indicating, for example, an elapsedtime from activation of the image display system 1. The time stamp fromthe server 7 and the time stamp from the inertial measurement unit 3 arematched with each other, for example, when the image display system 1 isactivated.

Additionally, information transmission from the server 7 to the terminalapparatus 8 may be performed using a communication scheme complying witha near field communication standard such as Bluetooth (registeredtrademark) or a communication scheme complying with a wirelesscommunication standard such as wireless Local Area Network (LAN).

The wireless communication is used between the server 7 and the terminalapparatus 8 as described above to prevent, when the server 7 and theterminal apparatus 8 are connected through a cable, the motion of theuser US wearing the terminal apparatus 8 from being obstructed by thecable.

[Configuration of Terminal Apparatus]

FIG. 4 is a block diagram illustrating a configuration of the terminalapparatus 8.

The different terminal apparatus 8 is provided for the respective usersUS and are each connected to the display apparatus 2 and the inertialmeasurement unit 3 through cables and wirelessly communicate with theserver 7. The terminal apparatus 8 can be configured using a PersonalComputer (PC) or the like and executes applications such as games. Forexample, the terminal apparatus 8 estimates the position and posture ofthe user US on the basis of information acquired from the inertialmeasurement unit 3 and the server 7, and outputs, to the displayapparatus 2, an image corresponding to the estimated position andposture. In other words, the terminal apparatus 8 is a type ofinformation processing apparatus and corresponds to a posture estimationapparatus.

As illustrated in FIG. 4, the terminal apparatus 8 as described aboveincludes a terminal section 81, an input section 82, an output section83, a communication section 84, a storage section 85, a memory 86, aGraphics Processing Unit (GPU) 87, and a Central Processing Unit (CPU)88, and these components are connected together through a bus line BL.

The terminal section 81 includes a plurality of terminals to whichcables connected to external apparatuses are connected. The terminalsprovided in the terminal section 81 include, for example,general-purpose connection terminals such as Universal Serial Bus (USB)terminals, and video terminals such as high-definition multimediainterface (HDMI (registered trademark)). In the present embodiment, theterminal section 81 includes a terminal 811 connected to the displayapparatus 2 and a terminal 812 connected to the inertial measurementunit 3.

The input section 82 corresponds to an acquisition section acquiringinformation input from any of the external apparatuses via the terminalsection 81. The input section 82 outputs the acquired information to theCPU 88 via the bus line BL. For example, the input section 82 acquiresdetection information from the inertial measurement unit 3 connected tothe input section 82 via the terminal 812, and outputs the acquireddetection information to the CPU 88.

Under the control of the CPU 88, the output section 83 outputsinformation input from the CPU 88 via the bus line BL, to a destinationexternal apparatus included in the external apparatuses connected to theterminal section 81. For example, the output section 83 outputs an imagedrawn by the GPU 87, to the display apparatus 2 connected to theterminal 811.

Under the control of the CPU 88, the communication section 84communicates wirelessly with any of the external apparatuses to transmitand receive information to and from the external apparatuses. Forexample, the communication section 84 communicates with the server 7 toreceive analysis information from the server 7 and output the receivedanalysis information to the CPU 88. In other words, the communicationsection 84, along with the input section 82, constitutes the acquisitionsection.

Communication by the communication section 84 as described above isperformed in compliance with the above-described communication scheme.

The storage section 85 stores programs and data for operations of theterminal apparatus 8. For example, the storage section 85 stores anOperating System (OS) and a game application, and also stores an errorcorrection program described below.

The memory 86 forms a work area for the GPU 87 and the CPU 88. Forexample, the memory 86 temporarily stores a part of the program storedin the storage section 85 and a part of the data stored in the storagesection 85.

The GPU 87 draws, under the control of the CPU 88, an image to be outputto the display apparatus 2, and corresponds to a drawing section.Specifically, the GPU 87 sets, in a virtual space developed by the CPU88 executing a game application, a viewpoint corresponding to theposition and posture of the user US identified by the CPU 88, and drawsan image of the virtual space from the viewpoint of the user US, on thebasis of a preset viewpoint and a preset light source. Thus, the drawnimage is read from the memory 86 and output to the display apparatus 2by the output section 83.

FIG. 5 is a block diagram illustrating a functional configuration of theCPU 88.

The CPU 88 executes the program stored in the storage section 85 tooperate the terminal apparatus 8. For example, the CPU 88 executes an OSstored in the storage section 85 to operate the terminal apparatus 8,and executes the game application stored in the storage section 85 tomove a game forward.

Besides, the CPU 88 estimates the position and posture of the user US inthe three-dimensional space SP on the basis of the detection informationinput from the inertial measurement unit 3 and the analysis informationreceived from the server 7, and sets, in the virtual space, a viewpointand a light source corresponding to the position and posture of the userUS. Additionally, the CPU 88 corrects, on the basis of the analysisinformation received from the server 7, the position and posture of theuser US calculated on the basis of the detection information from theinertial measurement unit 3.

As illustrated in FIG. 5, the CPU 88 as described above includes acalculation section 881, an estimation section 882, a setting section883, and a correction section 884.

The calculation section 881 sequentially adds, to an initial value,detection information input from the inertial measurement unit 3, andcalculates the position and posture of the user US based on thedetection information. Information indicating the position of the userUS calculated by the calculation section 881 is designated as calculatedposition information. Information indicating the posture of the user UScalculated by the calculation section 881 is designated as calculatedposture information. Information including the calculated positioninformation and the calculated posture information is designated ascalculated information. Note that the calculated posture informationcorresponds to second posture information and that the calculatedposition information corresponds to second position information.

Specifically, the initial value is detection information detected by theinertial measurement unit 3 when the user US is located at apredetermined position in the three-dimensional space SP and is in apredetermined posture. The calculation section 881 sequentially adds, tothe initial value, the detection information input from the inertialmeasurement unit 3 to calculate the calculated posture information andthe calculated position information.

Specifically, the calculation section 881 adds, to the last calculatedposture information, newly acquired detection information (particularlyan angular speed component) to calculate the latest calculated positioninformation. Additionally, the calculation section 881 adds, to the lastcalculated position information, newly acquired detection information(particularly an acceleration component) to calculate the latestcalculated position information.

Note that the detection information from the inertial measurement unit 3includes an error and thus that an error is included in the calculatedposture information and calculated position information calculated bythe calculation section 881. In particular, the angular speed used tocalculate the posture of the user US is detected by the gyro sensorincluded in the inertial measurement unit 3, but due to properties ofthe gyro sensor, sequential addition of detected angular speeds leads toaccumulated errors, increasing, over time, a deviation between theposture indicated by the calculated posture information and the actualposture of the user US.

Thus, the correction section 884 described below corrects the calculatedposture information and the calculated position information. Errorcorrection processing executed by the correction section 884 will bedescribed below in detail.

The estimation section 882 estimates the current position and currentposture of the user US in the three-dimensional space SP on the basis ofthe calculated posture information and calculated position informationas well as the analyzed posture information and analyzed positioninformation included in the analysis information received from theserver 7.

Specifically, the estimation section 882 estimates the current postureof the user US by synthesizing the received analyzed posture informationand the calculated posture information when the analysis information isreceived from the server 7. Similarly, the estimation section 882estimates the current position of the user US by synthesizing thereceived analyzed position information and the calculated positioninformation when the analysis information is received from the server 7.

Note that the calculated posture information and calculated positioninformation used to estimate the current position and current posture ofthe estimation section 882 correspond to the calculated postureinformation and calculated position information corrected by thecorrection section 884.

FIG. 6 is a diagram illustrating an input timing for the detectioninformation from the inertial measurement unit 3 and a reception timingfor the analysis information from the server 7. Note that the inputtiming for the detection information is illustrated in an upper stage ofFIG. 6 and that the reception timing for the analysis information isillustrated in a lower stage of FIG. 6.

In this case, since the inertial measurement unit 3 and the terminalapparatus 8 are connected through a cable, the detection informationfrom the inertial measurement unit 3 is periodically input to theterminal apparatus 8 as illustrated by vertical lines in the upper stageof FIG. 6. Note that an input rate for the detection information is 1000fps, which is equal to a sampling rate at which the acceleration and theangular speed are sampled by the inertial measurement unit 3.

On the other hand, the server 7 and the terminal apparatus 8 areconnected together for wireless communication. Thus, normally, theanalysis information from the server 7 is periodically received by theterminal apparatus 8 as illustrated by black circles in the lower stageof FIG. 6. A reception rate for the analysis information is 200 fps,which is equal to a sampling rate at which the analysis information issampled by the camera system 4.

However, factors such as a wireless environment may cause the analysisinformation to be received by the terminal apparatus 8 at a timing laterthan a normal reception timing. For example, in the lower stage of FIG.6, the analysis information, otherwise received at a timing illustratedby a white circle, may be received at a timing illustrated by a blackcircle later than the timing illustrated by the white circle.

In such a case, the estimation section 882 estimates the currentposition and the current posture on the basis of the newly receivedanalysis information and the calculated information includinginformation calculated by the calculation section 881 and corrected bythe correction section 884.

The setting section 883 illustrated in FIG. 5 sets a viewpoint in thevirtual space on the basis of the current position and current postureof the user US estimated by the estimation section 882. Accordingly, theGPU 87 draws an image corresponding to the viewpoint of the user US inthe virtual space on the basis of the set viewpoint and the preset lightsource. Note that the setting section 883 may set the position of thelight source in the virtual space in accordance with an operation by theuser US or the like.

Besides, the setting section 883 sets the input rate for the detectioninformation input from the inertial measurement unit 3, and sets thereception rate for the analysis information received from the server 7.Note that the input rate for the detection information and the receptionrate for the analysis information may be preset or may be acquired fromthe inertial measurement unit 3 and the server 7 and set.

FIG. 7 is a flowchart illustrating error correction processing executedby the correction section 884.

The correction section 884 corrects, on the basis of the analyzedposture information and analyzed position information included in theanalysis information, the calculated posture information and calculatedposition information calculated by the calculation section 881 on thebasis of the detection information. Specifically, the correction section884 corrects the calculated posture information and the calculatedposition information by implementing error correction processingillustrated in FIG. 7. The error correction processing is implemented bythe correction section 884 by executing the error correction programstored in the storage section 85.

In the error correction processing, first, the correction section 884resets a counter counting the number of pieces of detection informationinput (step SA1).

Then, the correction section 884 determines whether or not the currenttiming corresponds to the reception timing for the analysis information(step SA2). Specifically, in step SA2, the correction section 884identifies the reception timing for the next analysis information on thebasis of the set reception rate and the reception timing for theanalysis information received in the past, and determines whether or notthe current timing corresponds to the identified reception timing.

In a case of determining, in the determination processing in step SA2,that the current timing does not correspond to the reception timing(step SA2: NO), the correction section 884 repeatedly executes step SA2until the reception timing.

In a case of determining, in the determination processing in step SA2,that the current timing corresponds to the reception timing (step SA2:YES), the correction section 884 determines whether or not the analysisinformation has been received (step SA3). This processing takes intoaccount the possibility that reception of the analysis information isdelayed.

In a case of determining, in the determination processing in step SA3,that the analysis information has not been received (step SA3: NO), thecorrection section 884 counts the number of pieces of detectioninformation input before the analysis information to be received isreceived (step SA4) and returns the processing to step SA3.

In a case of determining, in the determination processing in step SA3,that the analysis information has been received (step SA3: YES), thecorrection section 884 acquires the calculated information calculated bythe calculation section 881 on the basis of detection informationincluding substantially the same time stamp as that included in thereceived analysis information (step SA5). Note that, in a case where nodetection information is present that includes the same time stamp asthat included in the received analysis information, the calculatedinformation is acquired that is based on the detection informationincluding a time stamp closest to the time stamp included in theanalysis information.

Then, the correction section 884 calculates an error between theanalysis information and calculated information acquired (step SA6).Specifically, the correction section 884 calculates a difference d1between the analyzed posture information and calculated postureinformation, and further calculates a difference d2 between the analyzedposition information and the calculated position information.Specifically, the correction section 884 acquires, as the difference d1,a value resulting from subtraction of the analyzed posture informationfrom the calculated posture information, and acquires, as the differenced2, a value resulting from subtraction of the analyzed positioninformation from the calculated position information.

Subsequently, the correction section 884 determines whether or not theabsolute value of the difference d1 for the posture is smaller than apreset threshold th1 (step SA7).

In a case where, in the determination processing in step SA7, theabsolute value of the difference d1 is equal to or larger than thethreshold th1 (step SA7: NO), the correction section 884 transfers theprocessing to step SA9. In a case where erroneous analyzed postureinformation is received from the server 7 for a reason such as erroneousmeasurement, the absolute value of the difference d1 is relativelylarge. Thus, in a case where the absolute value of the difference d1 isequal to or larger than the threshold th1, the correction section 884determines that erroneous analyzed posture information has beenreceived, and omits correction of the calculated posture informationbased on the analyzed posture information.

On the other hand, in a case where, in the determination processing instep SA7, the absolute value of the difference d1 is smaller than thethreshold th1 (step SA7: YES), the correction section 884 sets the“posture” as an error correction target (step SA8). Then, the correctionsection 884 transfers the processing to step SA9.

In step SA9, the correction section 884 determines whether or not theabsolute value of the difference d2 for the position is smaller than apresent threshold th2 (step SA9).

In the determination processing in step SA9, in a case where theabsolute value of the difference d2 is equal to or larger than thethreshold th2 (step SA9: NO), the correction section 884 transfers theprocessing to step SA11. As described above, in a case where theabsolute value of the difference d2 is equal to or larger than thethreshold th2, the correction section 884 determines that erroneousanalyzed position information has been received, and omits correction ofthe calculated position information based on the analyzed positioninformation.

In the determination processing in step SA9, in a case where theabsolute value of the difference d2 is smaller than the threshold th2(step SA9: YES), the correction section 884 sets the “position” as anerror correction target (step SA10). Then, the correction section 884transfers the processing to step SA11.

Note that the position of the user US can be relatively accuratelyestimated compared to the posture of the user US. Thus, to prevent theerror correction processing SB from being frequency executed for theposition, the threshold th2 is set to a smaller value than the thresholdth1.

In step SA11, the correction section 884 determines whether or not anyerror correction target has been set (step SA11). Specifically, in stepSA11, the correction section 884 determines whether or not the “posture”or the “position” has been set as an error correction target in stepsSA8 and SA10.

In a case of determining, in the determination processing in step SA11,that no error correction target is present, the correction section 884returns the processing to step SA1.

In a case of determining, in the determination processing in step SA11,that an error correction target is present, the correction section 884executes the error correction processing SB on the set error correctiontarget.

FIG. 8 is a flowchart illustrating the error correction processing SB.

In the error correction processing SB, the correction section 884 firstcalculates the number of loops as illustrated in FIG. 8 (step SB1).Specifically, the correction section 884 calculates, as the number ofloops, the integer value of a value obtained by subtracting the number βof pieces of detection information counted in step SA4 described abovefrom a value resulting from division of the input rate for the detectioninformation by the reception rate for the analysis information. Thisprocessing is intended to execute step B3 by the number of times ofdetection information input during a period from the reception timingfor the analysis information until the reception timing for the nextanalysis information. Note that, in a case where the analysisinformation is received at a normal reception timing, step SA4 is notexecuted and the number β of pieces of detection information is 0.

Then, the correction section 884 sets the loop counter n to 1 (stepSB2).

Subsequently, the correction section 884 corrects an error included inthe information set as the error correction target, that is, one of thecalculated posture information and the calculated position information(step SB3).

Specifically, in a case where the posture is set as the error correctiontarget, in step SB3, the correction section 884 corrects the latestcalculated posture information by subtracting a correction value C1indicated by Equation (1) from the latest calculated postureinformation. Note that, in Equation (1), d1 denotes the difference d1and that β denotes the number β of pieces of detection informationcounted in step SA4. R1 denotes the input rate for the detectioninformation, and r1 denotes the reception rate for the analysisinformation. α1 denotes a value indicating the degree of reflectionreferring to the degree to which the difference d1 is reflected in thecalculated posture information, that is, the degree to which thecalculated posture information is made closer to the analyzed postureinformation. α1 is larger than 0 and equal to or smaller than 1.However, in a case where R1/r1<β holds true, (R1/r1−β), which is thedenominator of the right side of Equation (1), is treated as 1.

[Math. 1]

Correction value C1=(d1×α1)/(R1/r1−β)  (1)

Additionally, in a case where the position is set as the errorcorrection target, in step SB3, the correction section 884 subtracts acorrection value C2 indicated by Equation (2) from the latest calculatedposition information. Note that, in Equation (2), d2 denotes thedifference d2. β, R1, and r1 are the same as β, R1, and r1 in Equation(1) described above. α2 denotes a value indicating the degree ofreflection referring to the degree to which the difference d2 isreflected in the calculated position information, that is, the degree towhich the calculated position information is made closer to the analyzedposition information. α2 is larger than 0 and equal to or smallerthan 1. Note that α2 may be the same as or different from α1. However,also in Equation (2), in a case where R1/r1<β holds true, (R1/r1−β),which is the denominator of the right side of Equation (2), is treatedas 1.

[Math. 2]

Correction value C2=(d2×α2)/(R1/r1−β)  (2)

For example, in a case where the number of loops is five, the number oftimes of step SB3 to be executed is five. In this case, each time stepSB3 is executed, the error included in the calculated postureinformation is corrected by (d1×α1)/5 and the error included in thecalculated position information is corrected by (d2×α2)/5.

Here, as described above, the calculation section 881 calculates thelatest calculated information for each input of the detectioninformation, and the estimation section 882 estimates the position andposture of the user US on the basis of the calculated latest calculatedinformation and analysis information. However, in a case where, forexample, step SB3 is executed a plurality of times before the inputtiming for the next detection information to significantly correct thecalculated information, the calculated information varies significantlyto cause significant variation in the estimated position and posture ofthe user US. In this case, an image drawn according to the position andposture of the user US varies significantly compared to the last image,causing the user to feel uncomfortable when viewing the image displayedby the display apparatus 2.

Thus, step SB3 is preferably executed with a cycle corresponding to theinput rate for the detection information. Specifically, step SB3 ispreferably executed once between the input timing for certain detectioninformation and the input timing for the next detection information.

Step SB3 executed as described above suppresses significant variation incalculated information before the input timing for the next detectioninformation, and thus suppresses the uncomfortable feeling of the user.

Additionally, even in a case where the following rates are high: adrawing rate at which the GPU 87 draws images, an output rate at whichimages are output to the display apparatus 2, and an update rate atwhich the display apparatus 2 updates images, the error in calculatedinformation is gradually corrected to enable reduction in differencebetween the last drawn, output, and displayed image and the image to bedrawn, output, and displayed next. Accordingly, also in this regard, theuser can be restrained from being uncomfortable.

Then, the correction section 884 determines whether or not the currentloop counter n has reached the number of loops (step SB4).

In a case of determining, in the determination processing in step SB4,that the loop counter n has not reached the number of loops (step SB4:NO), the correction section 884 increments the loop counter n by one(step SB5).

Subsequently, the correction section 884 returns the processing to stepSB3.

In a case of determining, in the determination processing in step SB4,that the loop counter n has reached the number of loops (step SB4: YES),the correction section 884 ends the error correction processing SB. Acorrection period when the error correction processing SB as describedabove is executed to correct the calculated information corresponds to aperiod from reception of the analysis information until the receptiontiming when the next analysis information is assumed to be received, asillustrated in FIG. 6.

In a case where the error correction processing SB ends, the correctionsection 884 returns the processing to step SA1 as illustrated in FIG. 7.In other words, the correction of the calculated information by thecorrection section 884 is repeatedly performed.

Note that, in a case where the difference d1 is equal to or smaller thanthe threshold th1, the difference d2 is equal to or smaller than thethreshold th2, and the error correction processing SB for the calculatedposture information and the error correction processing SB for thecalculated position information are each executed, the error correctionprocessing SB for the calculated posture information and the errorcorrection processing SB for the calculated position information may beseparately executed. Alternatively, after execution of one of the errorcorrection processing SB for the calculated posture information and theerror correction processing SB for the calculated position information,the other error correction processing SB may be executed.

Effects of Embodiment

The image display system 1 according to the present embodiment describedabove can produce the following effects.

The image display system 1 including the posture estimation systemincludes the inertial measurement unit 3, the markers 5, the camera 6,the server 7, and the terminal apparatus 8. The markers 5 are mounted onthe user US, which corresponds to an object. The camera 6 capturesimages of the user US. The analysis section 71 of the server 7 analyzesthe posture of the user US on the basis of the positions of the markers5 included in a captured image captured by the camera 6. The inertialmeasurement unit 3 used as the inertial measurement section is providedon the user US to detect motion of the user US.

The terminal apparatus 8 includes the calculation section 881, theestimation section 882, and the correction section 884. The calculationsection 881 calculates calculated posture information indicating theposture of the user US on the basis of the detection informationindicating a detection result from the inertial measurement unit 3. Theestimation section 882 estimates the actual posture of the user US onthe basis of the calculated posture information and the analyzed postureinformation indicating the posture of the user S analyzed by theanalysis section 71. The correction section 884 corrects an errorincluded in the calculated posture information on the basis of theanalyzed posture information.

Such a configuration can correct errors accumulated in the calculatedposture information calculated on the basis of the detection informationinput from the inertial measurement unit 3. Accordingly, the posture ofthe user US can be accurately estimated on the basis of the calculatedposture information and the analyzed posture information.

The analyzed posture information includes a time stamp indicating atiming of image capturing of a captured image for which analyzed postureinformation has been analyzed. The detection information includes a timestamp indicating the timing of detection of the user US motion by theinertial measurement unit 3. The correction section 884 corrects thecurrent calculated posture information on the basis of the analyzedposture information and the calculated posture information calculated onthe basis of detection information including substantially the same timestamp as that included in the analysis information.

Accordingly, the current calculated posture information is corrected onthe basis of the difference between the analyzed posture information andcalculated posture information each corresponding to substantially thesame posture of the user US. Thus, the calculated posture information,in which errors may be accumulated, can be appropriately corrected. Thisalso applies to the calculated position information.

The correction section 884 omits correction of the calculated postureinformation used as the second posture information in a case where theabsolute value of the difference d1 for the posture is larger than thethreshold th1. The correction section 884 corrects the calculatedposture information in a case where the absolute value of the differenced1 is equal to or smaller than the threshold th1.

Accordingly, in a case where the analyzed posture information receivedfrom the server 7 indicates an abnormal value, correction of thecalculated posture information based on this analyzed postureinformation can be inhibited.

Note that, in a case where the absolute value of the difference d2 forthe position is larger than the threshold th2, the correction section884 omits correction of the calculated position information, allowingproduction of effects similar to the above-described effects.

The correction section 884 corrects the calculated posture informationby repeatedly subtracting the correction value C1 indicated by Equation(1) described above from the calculated posture information, used as thesecond posture information, according to the number of pieces ofdetection information input from the time of reception of analysisinformation including the analyzed posture information until a timingassumed to receive the next analysis information.

Accordingly, the calculated posture information can be accuratelycorrected without dependence on an input state of the detectioninformation and a reception state of the analysis information.Furthermore, minor changes are reflected in the calculated postureinformation in a timely manner to suppress occurrence of a rapid changein the posture of the user US estimated by the estimation section 882.This also applies to the position of the user US estimated by theestimation section 882. This enables the display apparatus 2, on whichimages based on the estimated posture and position of the user US aredisplayed, to display images reflecting natural changes in the postureand position of the user US, allowing the user US to be restrained fromfeeling uncomfortable due to a rapid change in display contents.

The image display system 1 including the posture estimation system ismounted on the user US and includes the display apparatus 2, used as adisplay section displaying input images. The terminal apparatus 8includes the GPU 87, used as the drawing section drawing, in the virtualspace, an image from the viewpoint set according to the posture andposition of the user US estimated by the estimation section 882, and theoutput section 83 outputting, to the display apparatus 2, the imagedrawn by the GPU 87.

According to such a configuration, the posture and position of the userUS can be accurately estimated, thus allowing construction of a VRsystem that can present, in the virtual space, the user US with imagescorresponding to the viewing direction of the user US.

The image display system 1 used as the posture estimation systemincludes the server 7 used as an analysis apparatus acquiring capturedimages captured by the camera 6, and the terminal apparatus 8 providedon the user US, serving as the object, to acquire the detectioninformation from the inertial measurement unit 3, used as the inertialmeasurement section. The server 7 includes the analysis section 71, andthe terminal apparatus 8 includes the calculation section 881, theestimation section 882, and the correction section 884.

According to such a configuration, the functions can be shared betweenthe server 7 connected to the camera 6 and the terminal apparatus 8connected to the inertial measurement unit 3. Accordingly, thisconfiguration can reduce processing burdens compared to a configurationin which one apparatus includes the analysis section 71, the calculationsection 881, the estimation section 882, and the correction section 884.This allows a small terminal apparatus to be employed as the terminalapparatus 8 provided on the user US.

The terminal apparatus 8 communicates wirelessly with the server 7.Additionally, the terminal apparatus 8 communicates with the inertialmeasurement unit 3 through a cable.

In such a configuration, the inertial measurement unit 3, detectingmotion of the user US at a relatively high sampling rate and outputtingthe detection information, communicates with the terminal apparatus 8through the cable, and thus the terminal apparatus 8 can acquire thedetection information from the inertial measurement unit 3 withoutdelay. Additionally, since the server 7 and the terminal apparatus 8communicate wirelessly, the motion of the user US positioned in thethree-dimensional space SP can be prevented from being obstructed by thecable.

The terminal apparatus 8, used as a posture estimation apparatus,includes the input section 82, the communication section 84, thecalculation section 881, the estimation section 882, and the correctionsection 884. The communication section 84 receives, from the externalserver 7, the analyzed posture information (first posture information)indicating the analyzed posture of the user US. The input section 82receives the detection information indicating the detection result fromthe inertial measurement unit 3 provided on the user US. The calculationsection 881 calculates the calculated posture information (secondposture information) indicating the posture of the user US. Theestimation section 882 estimates the posture of the user US on the basisof the analyzed posture information and the calculated postureinformation. The correction section 884 corrects an error included inthe calculated posture information.

Additionally, the CPU 88 of the terminal apparatus 8, used as aninformation processing apparatus, implements the error correctionprocessing including the error correction method of correcting, on thebasis of the analyzed posture information (first posture information)received from the external server 7, an error included in the calculatedposture information (second posture information) indicating the postureof the user US calculated on the basis of the detection result from theinertial measurement unit 3 provided on the user US on the basis of theanalyzed posture information.

Additionally, the CPU 88 of the terminal apparatus 8 executes the errorcorrection program causing execution of the error correction processingSB including a correction step of correcting, on the basis of theanalyzed posture information (first posture information) received fromthe external server 7, an error included in the calculated postureinformation (second posture information) indicating the posture of theuser US calculated on the basis of the detection result from theinertial measurement unit 3 provided on the user US.

This allows production of effects similar to the effects of the imagedisplay system 1 used as the posture estimation system described above.

Modifications of Embodiment

The present disclosure is not limited to the above-described embodimentand includes modifications, improvements, and the like made to theembodiment to the extent that the object of the present disclosure canbe accomplished.

In the above-described embodiment, the image display system 1 includingthe posture estimation system detects, analyze, and estimates not onlythe posture of the user US, serving as the object, but also the positionof the user US. However, no such limitation is intended, and aconfiguration may be provided that estimates any one of the posture andposition of the user US. Note that, in a case where only the posture ofthe user US is estimated, a gyro sensor may be employed instead of theinertial measurement unit 3.

In the above-described embodiment, the terminal apparatus 8 communicateswirelessly with the server 7, used as the analysis apparatus. However,no such limitation is intended, and the server 7 and the terminalapparatus 8 may communicate through a cable. Similarly, the inertialmeasurement unit 3 and the terminal apparatus 8 may communicatewirelessly.

In the above-described embodiment, the analysis information includes thetime stamp for the timing of analysis of the position and posture of theuser US, and the detection information includes the time stamp for thetiming of detection of the user US motion. However, no such limitationis intended, in a case where the analysis information is received by theterminal apparatus 8 without delay, for example, in a case where theserver 7 and the terminal apparatus 8 are connected through a cable, notime stamp needs to be included in the analysis information or thedetection information. Note that some time may be required for theserver 7 to calculate the analysis information and that the timing oftransmission of the analysis information from the server 7 is assumed tobe different from the timing of image capturing and analysis of theposition and posture of the user US. Thus, in a case of a comparison ofthe analysis information and detection information resulting fromanalysis and detection at the same timing, the time stamps arepreferably included in the analysis information and the detectioninformation.

In the above-described embodiment, the calculated posture information isnot corrected in a case where the difference d1 for the posture islarger than the threshold th1, and the calculated position informationis not corrected in a case where the difference d2 for the posture islarger than the threshold th2. However, no such limitation is intended,and a configuration may be provided in which the correction section 884corrects the calculated posture information and the calculated positioninformation regardless of values of the differences d1 and d2.

In the above-described embodiment, the calculated posture information iscorrected by sequential subtraction of the correction value C1 indicatedby Equation (1) described above. Similarly, the calculated positioninformation is corrected by sequential subtraction of the correctionvalue C2 indicated by Equation (2) described above. However, no suchlimitation is intended, and the correction method for the calculatedposture information and the calculated position information may beappropriately changed as long as the calculated posture information iscorrected on the basis of the analyzed posture information and thecalculated position information is corrected on the basis of theanalyzed position information. For example, in a case where thedifference d1 is smaller than the threshold th1, the correctedcalculated posture information may be a value obtained by subtracting,from the calculated posture information, a value resulting frommultiplication of the difference d1 by the degree of reflection α1.Similarly, in a case where the difference d2 is smaller than thethreshold th2, the corrected calculated position information may be avalue obtained by subtracting, from the calculated position information,a value resulting from multiplication of the difference d2 by the degreeof reflection a2.

Additionally, for example, the correction section 884 may correct thecalculated posture information by setting, as the difference d1, a valueresulting from subtraction of the calculated posture information fromthe analyzed posture information, and adding, to the calculated postureinformation, the correction value C1 based on the difference d1. Thisalso applies to the correction of the calculated position information.

In the above-described embodiment, the image display system 1 includesthe display apparatus 2, and the terminal apparatus 8 includes the GPU87, used as the drawing section, and the output section 83 outputtingdrawn images. However, no such limitation is intended, and the displayapparatus 2, the GPU 87, and the output section 83 may be omitted. Evenin this case, a system can be configured such that the position andposture of the user US in the three-dimensional space SP can beaccurately estimated.

In the above-described embodiment, the user US is illustrated as theobject. However, no such limitation is intended, and a living organismother than human beings or a moving body such as a robot may beillustrated as the object.

In the above-described embodiment, the error correction processing isimplemented by the CPU 88 reading and executing the correction programstored in the storage section 85. However, no such limitation isintended, and the correction program may be recorded in a recordingmedium in a computer readable manner, and at the time of execution ofthe error correction processing, the CPU 88 may read the correctionprogram from the recording medium for execution. The recording mediummay be a disc type recording medium such as an optical disc, and a harddisk apparatus or a semiconductor memory can also be employed as therecording medium. Besides, the correction program may be acquired froman apparatus on the network. An information processing apparatusexecutes the correction program acquired as described above to allowproduction of effects similar to the effects of the terminal apparatus8.

In the above-described embodiment, the CPU 88 of the terminal apparatus8 executes the game application to proceed the game. Specifically, theimage display system 1 is a VR game system or an AR game system.However, the intended use of the image display system 1 is not limitedto the game. For example, the image display system 1 may be used for anexperience-type attraction or the like or may be a system providingimages of internal space of a museum, a display apartment, or the like.

In the above-described embodiment, the server 7 includes the analysissection 71 and is connected to the inertial measurement unit 3, and theterminal apparatus 8 communicating wirelessly with the server 7 includesthe calculation section 881, the estimation section 882, and thecorrection section 884. However, the analysis section 71 may notnecessarily be included in the server 7, and at least one of thecalculation section 881, the estimation section 882, and the correctionsection 884 may not be included in the terminal apparatus 8.

For example, the server 7 may include the analysis section 71, thecalculation section 881, the estimation section 882, and the correctionsection 884.

In this case, the server 7 may receive the detection information fromthe inertial measurement unit 3 wirelessly or through a cable. In a casewhere the server 7 wirelessly receives the detection information, theterminal apparatus 8 may wirelessly transmit, to the server 7, thedetection information input from the inertial measurement unit 3.

In this case, the server 7 may transmit, to the terminal apparatus 8,estimated information indicating the position and posture of the user USand estimated by the estimation section 882, and the terminal apparatus8 may draw an image based on the estimated information and output thedrawn image to the display apparatus 2.

On the other hand, in this case, the server 7 may include the settingsection 883 and the GPU 87, used as the drawing section, use the GPU 87to draw an image based on the position and posture of the user USestimated by the estimation section 882, and transmit the drawn image tothe display apparatus 2 wirelessly or through a cable.

Additionally, for example, the terminal apparatus 8 may include theanalysis section 71, the calculation section 881, the estimation section882, and the correction section 884. In this case, each of the pluralityof cameras 6 may transmit captured images to the terminal apparatus 8wirelessly or through a cable. Alternatively, a relay apparatusconnected to the plurality of cameras 6 may transmit captured imagesacquired from each camera 6, to the terminal apparatus 8 wirelessly orthrough a cable.

Alternatively, for example, the inertial measurement unit 3 may includethe calculation section 881 calculating the position and posture of theuser US on the basis of the detection information, and the calculatedinformation including the calculated position information and thecalculated posture information may be transmitted from the inertialmeasurement unit 3 to the terminal apparatus 8 or the server 7.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. A posture estimation system comprising: a markerthat is mounted on an object; a camera that captures an image of theobject; an analysis section that analyzes a posture of the object on abasis of a position of the marker included in a captured image capturedby the camera; an inertial measurement section that is provided on theobject to detect motion of the object; a calculation section thatcalculates calculated posture information indicating the posture of theobject on a basis of detection information indicating a detection resultfrom the inertial measurement section; an estimation section thatestimates the posture of the object on a basis of the calculated postureinformation and analyzed posture information indicating the posture ofthe object analyzed by the analysis section; and a correction sectionthat corrects an error included in the calculated posture information ona basis of the analyzed posture information.
 2. The posture estimationsystem according to claim 1, wherein the analyzed posture informationincludes a time stamp indicating a timing of image capturing of thecaptured image for which the analyzed posture information has beenobtained by analysis, the detection information includes a time stampindicating a timing of detection of motion of the object by the inertialmeasurement section, and the correction section corrects a current pieceof the calculated posture information on a basis of a difference betweenthe analyzed posture information and the calculated posture informationcalculated on a basis of the detection information including a timestamp substantially identical to the time stamp included in the analyzedposture information.
 3. The posture estimation system according to claim2, wherein the correction section does not correct the calculatedposture information in a case where an absolute value of the differenceis larger than a predetermined threshold, and the correction sectioncorrects the calculated posture information in a case where the absolutevalue of the difference is equal to or smaller than the predeterminedthreshold.
 4. The posture estimation system according to claim 2,wherein in a case of assuming that the difference is d1, that a degreeof reflection being a value larger than 0 and equal to or smaller than 1and being a degree to which the difference is reflected in thecalculated posture information is α1, that the number of pieces of thedetection information input from an assumed reception timing untilactual reception of the analyzed posture information is that an inputrate for the detection information is R1, and that a reception rate forthe analyzed posture information is r1, the correction section correctsthe calculated posture information by repeatedly subtracting acorrection value C1 indicated by Equation (1) from the calculatedposture information calculated by the calculation section according tothe number of pieces of the detection information input from a time ofreception of the analyzed posture information until a reception timingfor a next piece of the analyzed posture information.[Math. 1]Correction value C1=(d1×α1)/(R1/r1−β)  (1) However, in a case whereR1/r1<13 holds true, (R1/r1−β) is
 1. 5. The posture estimation systemaccording to claim 1, comprising: a display section that is mounted onthe object to display an input image; a drawing section that draws, in avirtual space, an image from a viewpoint set according to the posture ofthe object estimated by the estimation section; and an output sectionthat outputs, to the display section, the image drawn by the drawingsection.
 6. The posture estimation system according to claim 1, furthercomprising: an analysis apparatus that acquires the captured imagecaptured by the camera; and a terminal apparatus that is provided on theobject to acquire the detection information from the inertialmeasurement section, wherein the analysis apparatus includes theanalysis section, and the terminal apparatus includes the calculationsection, the estimation section, and the correction section.
 7. Theposture estimation system according to claim 6, wherein the terminalapparatus communicates wirelessly with the analysis apparatus, and theterminal apparatus communicates with the inertial measurement sectionthrough a cable.
 8. A posture estimation apparatus comprising: acommunication section that externally receives first posture informationindicating a posture of an object; an input section that receivesdetection information indicating a detection result from an inertialmeasurement unit provided on the object; a calculation unit thatcalculates, on a basis of the detection information, second postureinformation indicating the posture of the object; an estimation sectionthat estimates the posture of the object on a basis of the first postureinformation and the second posture information; and a correction sectionthat corrects, on the basis of the first posture information, an errorincluded in the second posture information.
 9. An error correctionmethod for correcting an error included in information indicating aposture of an object, the error correction method comprising:correcting, on a basis of first posture information indicating theposture of the object and externally received, an error included insecond posture information indicating the posture of the objectcalculated on a basis of a detection result from an inertial measurementunit provided on the object.